Control of a wind turbine taking fatigue measure into account

Abstract

The present invention relates to control of wind turbines where a fatigue load measure is taken into account. Control of a wind turbine is described where a control trajectory is calculated based on a fatigue load measure, the fatigue load measure being determined from a predicted operational trajectory. In embodiments the predicted operational trajectories are calculated by using a model predictive control (MPC) routine, and the fatigue load measure includes a rainflow count algorithm.

The invention claimed is: 
     
       1. A method of controlling a wind turbine, comprising:
 receiving a current operational state of the wind turbine; 
 based on the current operational state, calculating one or more predicted operational trajectories, the one or more predicted operational trajectories including a predicted control trajectory comprising a time series of at least one variable; 
 determining at least one predicted fatigue load measure from the one or more predicted operational trajectories, wherein the one or more predicted operational trajectories comprise a receding horizon trajectory with a prediction horizon, and wherein the at least one predicted fatigue load measure is determined for the prediction horizon; 
 determining fatigue experienced by the wind turbine for a plurality of time periods, over a past period, to determine a historic fatigue measure; 
 determining a current fatigue measure; 
 determining a control trajectory based on the current fatigue measure, the at least one predicted fatigue load measure, and the historic fatigue measure; and 
 controlling the wind turbine based on a first predicted value of the control trajectory. 
 
     
     
       2. The method according to  claim 1 , wherein the one or more predicted operational trajectories are calculated by optimizing at least one cost function, and wherein the at least one fatigue load measure is included in the cost function. 
     
     
       3. The method according to  claim 1 , wherein the one or more predicted operational trajectories are calculated by optimizing at least one cost function, and wherein the at least one fatigue load measure is included in the optimization as one or more constraints. 
     
     
       4. The method according to  claim 1 , wherein the at least one fatigue load measure includes a rainflow count algorithm. 
     
     
       5. The method according to  claim 4 , wherein the at least one fatigue load measure is based on a damage signal determined from a Palmgren-Miner sum. 
     
     
       6. The method according to  claim 1 , wherein the at least one fatigue load measure is based on spectral moments. 
     
     
       7. The method according to  claim 2 , wherein the cost function comprises a weighted element including the at least one fatigue measure. 
     
     
       8. The method according to  claim 7  wherein the weight is correlated with the historic fatigue measure. 
     
     
       9. The method according to  claim 2 , wherein an optimization criteria used to optimize the at least one cost function is an optimization criterion to keep the fatigue measure under a predefined level. 
     
     
       10. The method according to  claim 1 , wherein the current operational state of the wind turbine is obtained based on sensor readings from sensors arranged to measure sensor data relating to a physical state of the wind turbine. 
     
     
       11. A computer program product comprising software code adapted to control a wind turbine when executed on a data processing system, the computer program product being adapted to:
 receive a current operational state of the wind turbine; 
 based on the current operational state, calculate one or more predicted operational trajectories, the one or more predicted operational trajectories including a predicted control trajectory comprising a time series of at least one variable; 
 determine at least one predicted fatigue load measure from the one or more predicted operational trajectories, wherein the one or more predicted operational trajectories comprise a receding horizon trajectory with a prediction horizon, and wherein the at least one predicted fatigue load measure is determined for the prediction horizon; 
 determine fatigue experienced by the wind turbine for a plurality of time periods, over a past period, to determine a historic fatigue measure; 
 determine a current fatigue measure; 
 determine a control trajectory based on the current fatigue measure, the at least one predicted fatigue load measure, and the historic fatigue measure; and 
 calculate a control signal based on a first predicted value of the control trajectory to control the wind turbine. 
 
     
     
       12. A control system for a wind turbine, comprising:
 a controller arranged for receiving a current operational state of the wind turbine and based on the current operational state calculate one or more predicted operational trajectories, the one or more predicted operational trajectories including a predicted control trajectory comprising a time series of at least one variable; 
 wherein the controller system is further arranged to:
 determine at least one predicted fatigue load measure from the one or more predicted operational trajectories, wherein the one or more predicted operational trajectories comprise a receding horizon trajectory with a prediction horizon, and wherein the at least one predicted fatigue load measure is determined for the prediction horizon; 
 determine fatigue experienced by the wind turbine for a plurality of time periods, over a past period, to determine a historic fatigue measure; 
 determine a current fatigue measure; 
 determine a control trajectory based on the current fatigue measure, the at least one predicted fatigue load measure, and the historic fatigue measure; and 
 control the wind turbine based on a first predicted value of the control trajectory. 
 
 
     
     
       13. A wind turbine park controller arranged for controlling one or more wind turbines of a wind turbine park, the wind turbine park controller comprising:
 a controller arranged for receiving a current operational state of the wind turbine and based on the current operational state calculate one or more predicted operational trajectories, the one or more predicted operational trajectories including a predicted control trajectory comprising a time series of at least one variable; 
 wherein the controller system is further arranged to:
 determine at least one predicted fatigue load measure from the one or more predicted operational trajectories, wherein the one or more predicted operational trajectories comprise a receding horizon trajectory with a prediction horizon, and wherein the at least one predicted fatigue load measure is determined for the prediction horizon; 
 determine fatigue experienced by the wind turbine for a plurality of time periods, over a past period, to determine a historic fatigue measure; 
 determine a current fatigue measure; 
 determine a control trajectory based on the current fatigue measure, the at least one predicted fatigue load measure, and the historic fatigue measure; and 
 determine a control trajectory based on both the at least one predicted fatigue load measure and the historic fatigue measure; and 
 control the wind turbine based on a first predicted value of the control trajectory. 
 
 
     
     
       14. The method according to  claim 1 , further comprising:
 wherein the determining the fatigue experienced by the wind turbine for the plurality of time periods occurs as part of a monitoring operation of the wind turbine. 
 
     
     
       15. The method of  claim 1 , wherein determining fatigue experienced by the wind turbine comprises estimating fatigue experienced by the wind turbine based on one or more measured values.